Funds are requested in partial support of the second Conference on Folic Acid, Vitamin B12 and One-carbon Metabolism to be held under the auspices of the Federation at Copper Mountain, Colorado. A meeting on this topic was first held in 1986 (at Saxtons River, Vermont) and was very well received by the participants who included scientists from a variety of disciplines and from both basic science and clinical backgrounds. Discussion leaders for the nine sessions in the 1988 Conference have been selected, have all agreed to accept this role, and have obtained the consent of outstanding speakers to give presentations in their respective sessions. The detailed tentative program is presented, along with biographical sketches of the Chairman, Vice-chairman, and most of the Discussion Leaders and the speakers. Poster sessions will also be held. Participation will be limited to 150 and applicants will be selected on the basis of their expertise and interest as most likely to contribute to a stimulating and productive meeting. One major focus of the meeting will be on recent advances in the mechanistic understanding of enzymes with folate or cobalamin substrates. There will also be a session on the recent, significant studies of one-carbon metabolism in lower organisms. The ways in which such information may indicate new therapies of protozoal and other diseases will be discussed. The information will also be related to inherited disorders of the metabolism of folate, cobalamin and methionine. Finally, other sessions will consider the effects of drugs on folate and cobalamin metabolism and transport of these vitamin derivatives will also be discussed. A major objective of the Conference will be to bring together scientists with a number of different but related specific interests in order to promote communication and discussion that may lead to more integrated research in the general areas defined by the Conference topic.